The following graph shows on the P and S waves from an are the smaller ones, S b

Question

The following graph shows on the P and S waves from an are the smaller ones, S bottom find the distance from the earthquake earthquake (no surface waves: P waves waves are larger ones). Answer the questions and use the graph at 250 130 50 4. Find the difference between the P wave starting time and S wave starting time to determine the SP time gap (S time P time SP Gap) Seismic Wave Travel Times 5. Use the S-P line on the bottom graph to estimate the distance to the epicenter 14 12 10 Km S-P 6. CHALLENGE: Calculate the S-P gap and distance for the earthquake at the bottom (HINT: This graph DOES show surface waves). 2 (S time-P time = SP Gap) 0 10 20 30 40 50 60 70 80 90 100 Distance (Kilometers) distance to the epicenter Km WCN Vert SEP 12 (255), 1994 8 10 12 13 16 18 20 22 4 2 30 32 34 36 38 40 42 4 46 48 50

Explanation / Answer

5 As per the graph for 10 sec rise in time the distance is shifting 8 kilometers, therefore for a gap of 48 seconds the distance is as follows:

=(48/10) x 8

= 4.8 x 8

= 38.4 kilometres.

6.

SP gap = 12.9 - 5 = 7.9 seconds

Surface waves are Love wave(fastest surface wave and moves the ground from side-to-side. Confined to the surface of the crust, Love waves produce entirely horizontal) and Rayleigh wave(Rayleigh wave rolls along the ground just like a wave rolls across a lake or an ocean. Since most of the shaking felt from an earthquake is due to the Rayleigh wave, which can be much larger than the other waves)

Surface waves travel on surface hence distance can be calculated as:

Distance = speed of surface wave x time

= 5 x 25 (speed of surface wave = 5 km/s and time of love wave arrival is 25 sec)

Distance = 125 kilometers

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